So I was at a session, in which my character’s family amulet, which was already a magic item that gave me advantage on charisma checks against elves, was implanted into my character’s chest via the amulet just flying at me. It flew at my character because some merman or something I don’t know, stole it, and then, it flew up from out of the water. So now, not only do I have charisma advantage against elves, but I also have the ability to expend a hit dice to shift planes by plucking various strings in some sort of limbo dimension, or something. I’m not sure. Anyways, I can bring willing creatures with me, at the expense of an extra hit dice, and my character obviously has to wait before shifting again, because ya know, utilizing your magic to shift between a plane of existence, and bringing others with you, is tiring. Who would’ve guessed? This was part of a d100 roll on the second session that would either kill us or help us. We all rolled in the mid to high 90s, so everyone who attended that session (our Cleric, our Druid and I) all got boons. Our cleric received a godly great sword (he was a war cleric.) However, he died sacrificing himself to save the party. Our Druid got a leech in his brain, which is fairly complex, but I’ll simplify it for you. He gets an extra spell sheet for the leech, the leech cuts his life in half and has to be fed life force, and if the leech dies, the Druid dies. I should mention the Druid and Cleric got their boons on the second session. It took me until session 5, which was about a month and a half later. But hey, I can literally shift between planes of existence now. Worth it.

With that out of the way, were you ever given a magic item at some point in the campaign that changed or was given extra properties later in the campaign?

There is a group I watch where it's less about chance and more about deliberate evolution of the item. A weapon that has extra effects against Giant/kin can become more effective against Giant/kin if the attuned person attunes again while using a piece of a Giant/kin that was slain by or with the help of the weapon.

Only one part of one Giant/kin per encounter per day can be used in that way. (Say, 2 encounters in the same day: 1 encounter with 1 Giant, slain, and the other encounter with 2 Giant-kin, both slain. Only one piece of those three opponents can be used to attune a new ability into the weapon. If the player waits to attune the piece to the weapon at a later date, no other attunement can be done with the weapon on that specific later date, but the GM in question would probably require the player to preserve it or suffer social penalties due to carrying spoiling Giant/kin parts.)

That player being that player has thus far attuned one sensible piece from a cursed Frost Giant and one nonsensible (and, I might add, a little disturbing) piece from one of two adolescent male Hill Giants (who might not have necessarily been combatants if a dialog managed to open—and the player who can also speak Giant opted not to try for want of a piece to attune to the weapon).

homebrew, but the Order of the Gauntlet weapon in the pwyw pub in my sig block has a weapon that scales with faction renown. I enjoy that approach - similar to just scaling with level but different enough that i actually like it.